The document discusses methods for measuring and characterizing odors, including: - Measuring odor concentration using olfactometry and dilution methods to determine the European Odor Unit concentration. - Using an olfactometer and odor panelists to establish odor concentration through dilution and detection. - Categorizing odor intensity on a scale of 0 to 6. - Assessing odor hedonics on a scale from extremely unpleasant to extremely pleasant. - Characterizing odors verbally through descriptors provided by test subjects.

1. NEVROZ GÖSTERİCİ

2. The measurement of odor concentration is the most
widespread method to quantify odors. It is standardized in
CEN EN . The method is based on dilution of an odor
sample to the odor threshold (the point at which the odor is
only perceptible to 50 % of the test panel). The numerical
value of the odor concentration is equal to the dilution
factor that is necessary to reach the odor threshold. Its unit
is the European Odor Unit, OUE. Therefore, the odor
concentration at the odor threshold is 1 OUE by definition.

3. To establish the odor concentration, an olfactometer is used which employs a panel of
test persons. A diluted odorous mixture and an odor-free gas (as a reference) are
presented from sniffing ports to a group of panelists. In comparing the gases emitted
from each port, the panelists are asked to report the presence of odor. The gas-diluting
ratio is then decreased by a factor of 1.4 or two (i.e. the concentration is increased
accordingly). The panelists are asked to repeat their judgment. This continues for a
number of dilution levels. The responses of the panelists over a range of dilution
settings are used to calculate the concentration of the odor in terms of European Odor
Units (OUE/m3).

4. Olfactometer

5. Odor intensity can be divided into the following categories according to
intensity:
0 - no odor
1 - very weak (odor threshold)
2 - weak
3 - distinct
4 - strong
5 - very strong
6 - intolerable
This method is most often applied by having a dilution series tested by a panel
of independent observers who have been trained to differentiate intensity

8. Hedonic assessment is the process of scaling odors
on a scale ranging from extremely unpleasant via
neutral up to extremely pleasant. There is no
correlation between this method and the method
of measuring the odor intensity. However, the
hedonic perception of some odors may change
from pleasant to unpleasant with increasing
concentration and intensity.

9. This is a verbal characterization of the sensed odor by
the test person, such as
disgusting, caustic, ruffling, etc. There are no more
applications needed than a test person to run this
method. The evaluation of the odor type could be an
emission or an immission method. It has a great
impact on evaluating the source of the odor emission.

10. The following details have to be differentiated while the
emission is measured:
1st there is the odor time slice (Result = Part of “odor
hours per year” per area). Then there is the olfactory flag
scope (Result = Current scope at actual meteorology
situation). And last but not least there is the harassment
exaltation by questionings (Result = differentiated
acquisition harassments).

11. There are two main odor sampling techniques, the direct odor sampling and
the indirect odor sampling technique
Direct odor sampling
Air will be sampled at the source and fed straight into the olfactometer for
assessment by an odor panel. The following problems can be associated with this
technique:
Odor panel members need to be seated in an odor neutral environment, thus
they need to be housed in a separate area. This is difficult to achieve when
assessing odor released from, for example factories, where the odor can be
emitted from a stack on the end of a production line. This means that the odor
sample collected needs to be transported from the stack to the unit where the
odor panel sits. This can sometimes be on the other side of the factory plant. The
sample then must therefore pass through a very long sample line to the
olfactometer. This can have influences on the sample quality, can have potential
air blockages due to water condensation or other operational procedures.
Therefore most odor annoyance assessment companies use the indirect air
sampling method.

12. Indirect odor sampling is done with the use of odor (air)
sampling bags, which are made from an odor neutral material
e.g. Teflon. The odor sample bags are connected to an air
sampling line which is then, for example, hooked up to a stack.
The air stream is then sampled and stored in the odor sample
bag and can then be analyzed in a suitable environment (e.g. in
an odor laboratory).
The indirect method is used to sample a wide variety of odor
sources. From stacks on the end of a factory line, water
surfaces or ambient air surroundings.
Each odor source has its own set of problems when sampled;
these problems need to be overcome in order to collect a
representative sample of the odor source. The following
problems can be encountered:

13. Vacuum can be overcome by placing the odor sample bag in
vacuum container which can be placed under vacuum. If the
vacuum is higher than the vacuum at the source, the odor
sample will collect in the bag.

14. High temperatures and high moisture contents inside the odor
source leads to complications when sampled. When the
sample leaves the source, it will cool down and produce
condensate in the sample line and or odor sample bag. This
can lead to growth of bacteria or when drying out release more
odor, thus alter the odor concentration of the sample. The
same is true when sampling in high moisture conditions. A
way round the problem is to use a stack dilution probe through
which an inert gas (for example dry nitrogen) can be fed that
dries the sample stream. This prevents the moisture
condensing in the sample line and or the odor sample bag.

15. Sometimes odor sources emit a high concentration of
gases that are lethal to man. These samples must be
diluted to a safe level, before being presented to the odor
panel. This pre-dilution can be done in a stack-dilution
probe, by the addition of an inert gas or on a dilution
device for example an extra olfactometer.

16. More often than not, odor sampled at the source is higher than the ambient
odor concentration. In a few cases the odor concentration can be so high that
panelists will make a positive identification even if the olfactometer is diluting
the odor sample in its upper dilution range. The sample must then be pre-
diluted to make a sensible reading, this pre-dilution can again be done with a
stack-dilution probe, by the addition of an inert gas or on a dilution device for
example an extra olfactometer.

17. When a large surface is emitting odor, for example a sewage
treatment plant, a fixed dimension “hood” can be used. In
one end of the hood, clean air is blown in at a known
rate, and on the other end, a sample is collected via the
indirect method. If a large land surface is emitting odor, for
example a bio filter (a big concrete basin filled with wood
chip through which the factories waste air is pumped), a
section can be cornered off with plastic (e.g. Teflon) (of
which the dimensions are known). The air from the factory
will inflate the plastic (lift it up) and an odor sample can be
taken from under the plastic via the direct air method.